▎ 摘　　要

The absorption/amplification spectrum of terahertz radiation in inhomogeneous graphene (n-i-p-i structure) with a periodic dual metal grating is theoretically investigated. It is shown that the amplification of terahertz radiation sharply increases at the plasmon-resonance frequency, when losses due to electron scattering and emission are balanced by the plasmon gain (related to the stimulated radiative interband recombination of electron-hole pairs in the inverted region of graphene).